The present invention relates to a device for separating airborne particles, such as particles of an aerosol, into classes by grain size.
The devices which are currently available have been conceived to measure the distribution of the particles. In fact, these are instruments which separate the particles still in suspension in air (aerosol) and which collect them on a filter maintaining the separation. Upon deposition it is then possible to perform all the analyses required from time to time for industrial and environmental health, medical physics, and powder technology generally, to obtain grain size separation of the aerosol. Such devices generally comprise a channel of rectangular section and of L-shape form through which filtered air passes; the particle-bearing air is injected into the first part of the channel upstream of the curvature which separates the first part from the second; upon passing the sharp curvature of the channel the particles tend by inertia to maintain their velocity in sense and direction, but are carried along by the flow. The particles having the same dimension become disposed in the same streamline which comes into contact with a well defined region of the filter; therefore such particles are separated from the initial flow of fluid by a distance which is a function only of aerodynamic diameter and the filter collects the particles which are arranged in different positions according to their aerodynamic dimensions.